I was on my way home, and just before entering the last roundabout, I heard a loud scraping noise (not metallic, more like a 'plastic scraping' sound) and felt some vibrations in the car. I pulled over, turned off the engine, and started it again. The loud 'plastic noise' was gone, but I noticed that the fan wasn't blowing through the vents—there was neither cold nor hot air coming out. I immediately thought the cabin blower fan was broken. However, I turned the engine off and on once more, and then everything went back to normal—meaning no plastic noise, and cold air was blowing through the vents again.

But I opened the hood and noticed a sound I didn't recognize: https://www.youtube.com/shorts/HpBd58aZ32c

It's hard to describe, but it reminds me of the sound of a VW Beetle accelerating, or some sort of relay/electrical buzzing. And I'm pretty sure that the sound comes from breake-fluid refilcap area.

Where is this sound coming from, and could it be connected to the fan suddenly stopping?

8 hours ago, B0sko said:

Where is this sound coming from, and could it be connected

Does it make the sound with engine turned off. Might be easier to answer if we can hear it with the engine turned off